The molecular breeding technology of crops makes it possible to use the genes of all species as breeding materials and to regulate the effects of breeding minutely at the gene level instead of at the genome level as in the past. Therefore it is one of the core technologies leading into the next generation of agriculture.
In order to maximize the effects of such molecular breeding technologies of crops, the essential prerequisites are as follows:
1) the accumulation of a database of genes to represent various plants;
2) the establishment of transformation systems for various crops; and
3) the development of promoters that regulate the expression of foreign genes inserted into plants.
In foreign countries promoters regulating the expression of plant genes have been studied since the early 1980's. It was suggested that a promoter of cauliflower mosaic virus could induce high levels of gene expression in all kinds of plant tissues (Hohn et al., 1982, Curr. Topics Microbiol. Immunol. 96: 193-236).
Subsequently, the sequence of the promoter was identified (Odell et al., 1985, Nature 313:810-812). It was proved that the promoter could induce high levels of gene expression in plants (Sanders et al., 1987, Nucleic Acids Res. 15: 1543-58). Since then, CaMV 35S promoter (Patent NO.: JP1993192172-A1) has become the most universal promoter used in plants.
Since the identification of CaMV 35S, promoters expressing genes in specific plant tissues have been actively studied. The specific studies relating to the promoters expressing genes in specific plant tissues are as follows.